The present invention relates to a defrosting device for a refrigerator comprising a number of cooling compartments, of which at least one is used for storing fresh food and at least a second for storing frozen food, at least a first evaporator assigned to the fresh food compartment and at least a second evaporator assigned to the freezer, both with refrigerating fluid flowing through them in a series circuit, a compressor for compressing the refrigerating fluid, a condenser for condensing the refrigerating fluid from the compressor, a system of capillary tubes for supplying the refrigerating fluid from the condenser to the evaporators and at least one return pipe connecting the evaporators to the inlet on the compressor.
On known types of refrigerators with a number of cooling compartments, the fresh food compartment evaporator is defrosted at each cooling cycle by an electric resistor which is kept running as long as the compressor is off.
In other words, the complete cooling cycle on current refrigerators with more than one cooling compartment is as follows: when the fresh food compartment evaporator reaches a given maximum temperature, the compressor is started up. When the temperature of the said fresh food compartment evaporator falls to a given minimum, however, the compressor is turned off and, at the same time, the defrosting resistor turned on to heat the said fresh food compartment evaporator back up to maximum temperature. When the latter is reached, the defrosting resistor is turned off and the compressor turned back on to commence another cooling cycle.
The sole purpose of all this is to avoid too long a lapse of time between the fresh food compartment reaching minimum temperature and the compressor being started up again, which could happen if the system depended solely on natural defrosting. Should the compressor take too long to start up, the temperature in the freezer could exceed the allowed maximum with consequent damage to the foodstuffs stored inside.
The drawback on this defrosting system, however, is its crude design which results in twice the necessary waste in energy. At each cooling cycle, the refrigerator is supplied with heat the production of which requires the consumption of electricity for heating the defrosting resistor. This heat must then be extracted from the said refrigerator which means extra work for the compressor and further consumption of electricity.